Conventional internal combustion engines may be equipped with a particulate filter, which is located in an exhaust pipe of the engine to retain and remove soot from the exhaust gas. During the normal operation of the engine, an electronic control unit (ECU) is generally provided for estimating an overall quantity of soot which is stored into the particulate filter and for activating a regeneration of the particulate filter, when the overall quantity of soot exceeds a maximum allowable amount thereof. The regeneration is generally achieved by operating the internal combustion engine in such a way to increase the temperature of the particulate filter up to a value that triggers the combustion of the accumulated soot.
To estimate the overall quantity of soot stored into the particulate filter, the ECU needs to know the residual quantity of soot that was still present into the particulate filter at the end of last regeneration. This residual quantity of soot may be determined by the ECU in several different ways, one of which provides for determining, during the regeneration, the temperature and the mass flow rate of the exhaust gas at the inlet of the particulate filter. These parameters are then used as input of a calibration model that provides as output an estimation of a temperature inside the particulate filter. The estimated temperature is finally used to estimate the residual quantity of soot. However, the temperature estimation provided by the calibration model may be affected by a margin of error which is not always negligible, with the consequence that sometimes the estimation of the residual soot quantity and the correlated estimation of the overall soot quantity are not completely reliable.
To compensate for this unreliability, the maximum allowable level of soot that triggers the regeneration of the particulate filter must be maintained relatively small, thereby avoiding uncontrollable burning of soot but also increasing the number of regenerations and thus the fuel consumption and oil dilution.